Abstract

Synthesis of ribosomal RNA (rRNA) by RNA polymerase (Pol) I is the first step in ribosome biogenesis and a regulatory switch in eukaryotic cell growth. Here we report the 12 A cryo-electron microscopic structure for the complete 14-subunit yeast Pol I, a homology model for the core enzyme, and the crystal structure of the subcomplex A14/43. In the resulting hybrid structure of Pol I, A14/43, the clamp, and the dock domain contribute to a unique surface interacting with promoter-specific initiation factors. The Pol I-specific subunits A49 and A34.5 form a heterodimer near the enzyme funnel that acts as a built-in elongation factor and is related to the Pol II-associated factor TFIIF. In contrast to Pol II, Pol I has a strong intrinsic 3'-RNA cleavage activity, which requires the C-terminal domain of subunit A12.2 and, apparently, enables ribosomal RNA proofreading and 3'-end trimming.

Related References

In this issue, Kuhn et al. (2007) report the complete structure of the 14-subunit yeast RNA polymerase (Pol) I enzyme at 12 A resolution using cryo-electron microscopy (cryo-EM). Their study reveals that three subunits of Pol I perform functions in transcription elongation that are outsourced to the transcription factors TFIIF and TFIIS in the analogous Pol II transcription system.

Interaction Annotations

Increase the total number of rows showing on this page by using the pull-down located below the table, or use the
page scroll at the table's top right to browse through the table's pages; use the arrows to the right of a column
header to sort by that column; filter the table using the "Filter" box at the top of the table; click on the small
"i" buttons located within a cell for an annotation to view further details about experiment type and any other
genes involved in the interaction.

Gene Ontology Annotations

Increase the total number of rows showing on this page using the pull-down located below the table, or use the page
scroll at the table's top right to browse through the table's pages; use the arrows to the right of a column header
to sort by that column; filter the table using the "Filter" box at the top of the table.

Phenotype Annotations

Increase the total number of rows showing on this page using the pull-down located below the table, or use the page
scroll at the table's top right to browse through the table's pages; use the arrows to the right of a column header
to sort by that column; filter the table using the "Filter" box at the top of the table; click on the small "i"
buttons located within a cell for an annotation to view further details.

Regulation Annotations

Increase the total number of rows displayed on this page using the pull-down located below the table, or use the
page scroll at the table's top right to browse through the table's pages; use the arrows to the right of a column
header to sort by that column; to filter the table by a specific experiment type, type a keyword into the Filter box
(for example, “microarray”); download this table as a .txt file using the Download button or click Analyze to
further view and analyze the list of target genes using GO Term Finder, GO Slim Mapper, SPELL, or YeastMine.

Expression Datasets

Increase the total number of rows displayed on this page using the pull-down located below the table, or use the
page scroll at the table's top right to browse through the table's pages; use the arrows to the right of a column
header to sort by that column; filter the table using the "Filter" box at the top of the table; download this table
as a .txt file using the Download button;